.\" RCSid "$Id: ra_t8.1,v 1.3 2004/03/26 22:58:20 greg Exp $"
.TH RA_T8 1 5/30/95 RADIANCE
.SH NAME
ra_t8 - convert RADIANCE picture to/from Targa 8-bit image file
.SH SYNOPSIS
.B ra_t8
[
.B \-d
][
.B \-b
][
.B "\-c ncolors"
][
.B "\-g gamma"
][
.B "\-e +/-stops"
][
.B "-n sampfac"
]
.B input
[
.B output
]
.br
.B ra_t8
.B \-r
[
.B "\-g gamma"
][
.B "\-e +/-stops"
]
[
.B input
[
.B output
]
]
.SH DESCRIPTION
.I Ra_t8
converts between RADIANCE and Targa 8-bit color-mapped image files
(type 1 in Targa's documentation).
In the default mode, a RADIANCE picture is converted to a
color-mapped Targa file of the same horizontal and vertical dimensions with
8-bits per pixel.
The
.I \-d
option turns off dithering.
The
.I \-b
option converts the image to black and white.
Only with this option can the input be taken from stdin.
The
.I \-c
option allows fewer than 256 colors.
The
.I \-g
option specifies the exponent used in gamma correction;
the default value is 2.2.
An exponent of 1.0 turns gamma correction off.
The
.I \-e
option specifies an exposure compensation in f-stops (powers of two).
Only integer stops are allowed, for efficiency.
The
.I \-n
option specifies a sampling factor for neural network color
quantization.
This value should be between 1 and 80, where 1 takes the longest and
produces the best results in small areas of the image.
If no value is given, a faster median cut algorithm is used.
The
.I \-r
option invokes a reverse conversion, from an 8-bit Targa file to
a RADIANCE picture.
If the output file is missing, the standard output is used.
.SH AUTHORS
Greg Ward
.br
Anthony Dekker provided the code for neural network color quantization
.SH BUGS
Run-length encoded files can be read but not written with this
program.
.SH "SEE ALSO"
pfilt(1), ra_bmp(1), ra_bn(1), ra_ppm(1), ra_pr(1), ra_pr24(1), ra_t16(1),
ra_tiff(1), ximage(1)
